RFR: JDK-8225140: Build fails if directory contains 'unix'

[Tim Bell]

Erik:

> This patch changes the filter mechanics to only apply to the path
> relative to the workspace root. I also changed the filter token from
> "unix" to "/unix/" to avoid the risk of matching substrings in
> directories in the future.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8225140
>
> Webrev: http://cr.openjdk.java.net/~erikj/8225140/webrev.01/index.html

Looks good.

Tim